1. Technical Field
This invention relates generally to gas turbine engines and particularly to a device for balancing the rotors of such gas turbine engines.
2. Background Information
Gas turbine engines such as those which power aircraft and industrial equipment such as electrical generators, pumps and the like employ bladed rotors disposed within stators which include components such as vanes and seals. The stators are typically mounted within an outer case. It is a well-known practice to balance the engine rotors in the manufacture and assembly of the engines. Such rotor balancing minimizes the deleterious effects of rotor vibrations caused by imbalances in the rotors due to the normal tolerances in the manufacture of rotor components or anomalies in such manufacture.
It is also a well-known practice to balance the engine's rotors during the operational life of the engine. Such balancing during the operational life of the engine is necessary to correct imbalances in the engine's rotor due to normal rotor wear, bowing of the rotor, and erosion of the components thereof due to the ingestion of foreign matter during operation. Known methods of balancing a gas turbine engine rotor include the testing of the rotor to determine the location and magnitude of any imbalances, followed by the addition of weight to, or removal of weight from, the rotor at the location of the imbalance to remove the imbalance.
Typically, balancing a gas turbine engine rotor at, for example, a compressor section thereof is accomplished by adding weights to the rotor by attaching small weights to the rotor at compressor blade hubs or disks with clips or other mounting hardware, or removal of weight from the hubs or disks by grinding or similar material removal techniques. Access to the location on the engine's rotor where weight addition or removal is necessary to achieve balancing is typically through small ports located in the engine's case. However, such ports usually provide a very limited area for insertion and removal of tooling necessary to add weight or remove material from the rotor. Furthermore, accessing the rotor through such ports in the engine's case requires circumvention of components in the engine's stator by tooling required for weight addition or removal, and therefore addition or removal of weight from a gas turbine engine's rotor to achieve a balancing thereof requires removal of the rotor from the interior of the stator and case, as well as removal of various components of the engine's stator. Such engine teardowns associated with certain prior art balancing techniques and systems are costly and time consuming and can add significantly to the cost of and time required for balancing an engine's rotor in the manufacture and assembly thereof or the maintenance thereof in the field.
Accordingly, there is a need for a gas turbine engine rotor trim balance by which weight may be conveniently and efficiently added to or removed from a gas turbine engine rotor to achieve balancing thereof in the manufacture and the assembly thereof as well as in field maintenance thereof.